The present invention relates to an improvement in a diaphragm-type pumping apparatus comprising: a main body section operatively supporting a center rod so as to allow a reciprocating motion thereof. The center rod is provided with a pair of diaphragms attached to both sides thereof respectively. A pair of casing members arranged so as to hold the main body section from opposite sides, which function in association with the main body section to clamp peripheral portions of respective diaphragms from the opposite sides along a thickness direction thereof. The fluid is sucked through a fluid suction port and discharged from a fluid discharge port by reciprocating the center rod.
As for a diaphragm-type pumping apparatus, such an apparatus has been known that comprises: a pair of disc-like diaphragms, each having a diaphragm section for defining a fluid delivering chamber and a working fluid chamber; a main body section operatively supporting a center rod so as to allow a reciprocating motion thereof, each of said diaphragms being mounted at a central portion thereof to each end of said center rod respectively; and a pair of casing members having communicating channels formed therein for providing a communication between a fluid suction port and a fluid discharge port via a fluid delivering chamber and being arranged so as to hold said main body section from opposite sides to function in association with said main body section for clamping peripheral portions of said respective diaphragms from opposite sides along a thickness direction thereof (see, for example, the Japanese Patent Publication No. Hei 6-31650).
In this conventional diaphragm-type pumping apparatus, typically, working fluid is supplied to one working fluid chamber located in one diaphragm side and to the other working fluid chamber located on the other diaphragms side alternately, and in response to this change-over in supply of the working fluid to those two working fluid chambers, the center rod is reciprocated so as to induce a volume expansion of the one working chamber and that of the other working chamber alternately, so that the fluid can be sucked from a fluid suction port into respective fluid delivering chambers alternately thus to exhaust the fluid, which has been sucked into respective fluid delivering chambers, from respective fluid delivering chambers alternately, thereby discharging the fluid from the fluid discharge port successively.
In this conventional diaphragm-type pumping apparatus, the peripheral portions of respective diaphragms are clamped between the main body section and the respective casing members disposed in opposite sides thereof, in which the main body section and a pair of casing members are fastened together along the thickness directions of the diaphragms with tie rod screw members so as to clamp the peripheral portions of the diaphragms between the casing members and the main body section.
Accordingly, there has been a problem due to this configuration in that, if Teflon (registered trademark) is used as a material of the casing member, a degree of expansion and contraction thereof in association with the temperature change would be large because Teflon (registered trademark) material itself has a greater coefficient of linear expansion as compared to a metal, and consequently, in the conventional configuration in which the peripheral portions of the diaphragms are simply clamped along its thickness direction in the clamping portions between a pair of casing members and the main body section by the tie rod screw members, it is likely to cause a looseness in the clamping portions, resulting in leakage of the working fluid or the fluid to be delivered, from the clamping portions to the outside.
That is, since Teflon (registered trademark) material is soft and apt to be deformed in the range of the room temperature (23xc2x0 C.) but in contrast the tie rod screw member is made of stainless steel, and accordingly, even if a pair of casing members and the main body section are clamped and fastened together as three in one body with tie rod screw members under the room temperature environment, when the temperature drops in the operational environment, the casing member would be contracted along an extending direction of the tie rod screw member by an amount greater than the contracting amount of the tie rod screw member, there would occur such an apparent condition that the fastening of the pair of casing members and the main body section by the tie rod screw members has been loosened, resulting in a problem that a gap is produced in the clamping portion of the diaphragm, through which the working fluid or the fluid to be delivered leaks to the outside.
To overcome this problem, when the diaphragm-type pumping apparatus is to be operated in an operational environment of lower temperature, the tie rod screw members are further tightened to increase the fastening force between the pair of casing members and the main body section before starting the operation of the apparatus. However, since the casing member is expanded more than the tie rod screw member along the extending direction of the tie rod screw member when the temperature rises in the operational environment, the fastening force between the casing members and the main body section also rises up to an excessively tightened condition and thereby the casing member is deformed, which might shorten the life-time of the diaphragm-type pumping apparatus.
Further, this diaphragm-type pumping apparatus also involves another problem in that, due to the looseness induced in the clamping portion where the peripheral portion of the diaphragm is clamped, the peripheral portion of the diaphragm sometimes slips so as to be pulled out of the clamping portion during the reciprocating motion of the center rod, resulting in a breakdown of the apparatus.
The present invention has been made in the light of the circumstances described above, and an object thereof is to provide a diaphragm-type pumping apparatus which can prevent the working fluid or the fluid to be delivered from being leaked through the clamping portion for clamping the peripheral portion of the diaphragm between the main body section and the casing member while preventing the peripheral portion of the diaphragm from being pulled out of the clamping portion between the main body section and the casing member during the reciprocating motion of the center rod thus to extend the life of the apparatus.
According to the present invention, there is provided a diaphragm-type pumping apparatus comprising: a pair of disc-like diaphragms, each having a diaphragm section for defining a fluid delivering chamber and a working fluid chamber; a main body section operatively supporting a center rod so as to allow a reciprocating motion thereof, said pair of diaphragms being attached at central portions thereof to respective ends of said center rod; and a pair of casing members arranged so as to hold said main body section from opposite sides thereof and functioning in association with said main body section to clamp peripheral portions of said respective diaphragms from opposite sides along a thickness direction thereof, in which a fluid is sucked through a fluid suction port and discharged from a fluid discharge port by reciprocating said center rod in response to a change-over in supplying a working fluid to said respective working fluid chambers.
The diaphragm-type pumping apparatus is characterized in that the casing member is made of Teflon (registered trademark) material. The diaphragm has an annular lip section formed in an outer circumferential portion defined so as to be further outside of a peripheral portion thereof and extends along a direction of a reciprocating motion of said center rod and also along a thickness direction of the diaphragm. Also, either one of the casing member or the main body section is provided with an annular wall section, which forms an annular recess for accommodating an ingress of the annular lip section.
Also, according to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus in which the casing member has a communicating channel formed therein for providing a communication between the fluid suction port and the fluid discharge port via said fluid delivering chamber.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which the main body section has a communicating channel formed therein for providing a communication between the fluid suction port and the fluid discharge port via the fluid delivering chamber.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which a threaded section is formed on a outer surface of the annular wall section, and an annular threaded member is engaged with the threaded section for compressing the annular lip section toward a clamping portion between the main body section and the casing member.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which the annular recess is formed such that an approach channel for the annular lip section is made to be narrower gradually from an entrance port toward an innermost portion thereof.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which the annular threaded member has a compressing wall section for compressing the annular lip section directly or indirectly along a thread traveling direction for pushing the annular lip section into the annular recess.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which the diaphragm is made of Teflon (registered trademark).
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which a cylinder section is formed in a central portion of the diaphragm and further a threaded section is formed on an inner surface of the cylinder section so as to be engaged with a threaded section of the center rod, and another threaded section is formed on an outer surface of the cylinder section. Also, a reinforcing ring member is engaged with the threaded section formed on said outer surface of the cylinder section so as to clamp the cylinder section in association with said center rod from either side, and the center rod is made of PPS.
According to another aspect of the present invention, there is provided a diaphragm-type pumping apparatus, in which the reinforcing ring member is made of PP or PVC.
According to another aspect of the present invention as defined in claim 10, there is provided a diaphragm-type pumping apparatus, in which an O-ring is arranged in a contact location of the main body section with the annular lip section.